[OSM-talk] What do you wish you'd known?
teemu.koskinen at mbnet.fi
Sat Mar 20 10:00:01 GMT 2010
On Sat, 20 Mar 2010 11:50:13 +0200, John Smith <deltafoxtrot256 at gmail.com>
> On 20 March 2010 19:42, Teemu Koskinen <teemu.koskinen at mbnet.fi> wrote:
>> I wish I had known that the Yahoo aerial images are not rectified, as I
>> blindly went and "corrected" all the roads in my neighborhood by moving
>> them to coincide with the aerial images. In reality they already were in
>> the correct position as they were drawn from more accurate gps-traces.
> Someone mentioned this a while back, in terms of editors storing
> corrected image positions centrally.
That only helps if the images are just offset by some amount, it doesn't
help at all if they are warped, rotated etc.
See eg. the centre of Helsinki: http://elanor.mine.nu/daeron/wavy.jpg
All the red lines are completely straight in reality. The whole Helsinki
area is full of similar errors in the Yahoo aerial images.
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